php - laravel 迁移 :rollback wrong

Question

Laravel 版本 5.1.43(LTS)

我在终端中使用 php artisan migrate:rollback 然后返回错误信息。但是数据库变了。然后我再次重新输入此命令，没有错误消息。

谁能帮我解决这个问题？

[Illuminate\Database\QueryException] SQLSTATE[42000]: Syntax error or access violation: 1091 Can't DROP'user_id'; check that column/key exists (SQL: alter table crm_user drop index user_id)

[PDOException] SQLSTATE[42000]: Syntax error or access violation: 1091 Can't DROP 'user_id'; check that column/key exists

我的迁移代码

public function down()
{
    if (Schema::hasColumn('crm_user', 'user_id')) {
        Schema::table('crm_user', function (Blueprint $table) {
            $table->dropColumn('user_id');
            $table->dropIndex('user_id');
        });
    }
}

Answer 1

当您删除您的列时，您的索引会自动删除。因此，当您尝试单独删除索引时，您会收到它不存在的错误。

所以要么交换顺序，然后先删除索引:

$table->dropIndex('user_id');
$table->dropColumn('user_id');

或者直接删除列，不用担心索引。

来自 MySQL 手册:

If columns are dropped from a table, the columns are also removed from any index of which they are a part. If all columns that make up an index are dropped, the index is dropped as well.